The present invention relates generally to fastener driving tools, and more specifically to such a tool having a pre-pressurized power delivery source.
Power tools for use in driving fasteners into work pieces are known in the art. Such tools can be operated by a variety of power sources, including pneumatic, combustion, electric or powder-activated power sources. In some power tools, the power source is integrated with a housing of the tool for easy portability. Other applications require power to be fed with a feed line from an external source, such as pneumatic tools operated by an air compressor.
Fastener driving tools of this type, and particularly pneumatically powered tools, include a metal housing and a magazine portion that is attached to the housing and/or the handle. Generally, the magazine retains a supply of fasteners which are fed to a drive track in the housing configured for receiving and guiding a fastener as it is driven by a reciprocating piston and driver blade from the drive track into a work piece.
A suitable pneumatically powered fastener-driving tool with a portable power source is disclosed in U.S. Pat. No. 6,876,379, which is incorporated by reference. In such a tool, the tool housing defines a main chamber having a cylinder for accommodating reciprocation of the driver blade and piston. The driving stroke of the piston moves a driver blade in the drive track that impacts a fastener to drive the fastener into a work piece. The piston is powered by a pneumatic power source, most preferably a portable container or vessel of compressed gas such as carbon dioxide or the like, which forces the piston in a driving direction under operator control through pulling of a trigger. The piston also configured to be oppositely driven by a partial vacuum or other known apparatus in a return stroke to the retracted or pre-driving position.
One drawback of conventional tools of this type is that the mechanical mechanism used to trigger and power the fastener driving power cycle is relatively inefficient in the use of the limited supply of compressed gas. A main result is that the operational life of such tools is relatively short and unacceptable to many users. As such, this type of tool has had a limited commercial application.